body {
    font-family: "方正品尚黑简体", "极限丽黑", "微软雅黑", "Helvetica Neue", Helvetica, Arial, sans-serif;
    padding: 30px;
}

form {
    margin-left: auto;
    margin-right: auto;
    text-align: center;
    width: 220px;
    margin-top: 100px;
}

#submit {
    float: right;
}

.form-signin-heading {
    text-align: left;
}

.back {
    float: left;
}

.input-big {
    width: 236px;
}